﻿88 
  J. 
  D. 
  Dana 
  — 
  features 
  of 
  non-volcanic 
  Igneous 
  Ejections. 
  

  

  era 
  one, 
  a, 
  contains 
  chiefly 
  prehnite, 
  with 
  traces 
  of 
  copper 
  ore, 
  

   and 
  the 
  trap 
  along 
  its 
  course 
  is 
  solid 
  or 
  little 
  altered. 
  The 
  

   other 
  is 
  situated 
  about 
  half 
  way 
  between 
  the 
  sides. 
  It 
  con- 
  

   tains 
  abundantly 
  the 
  very 
  hydrous 
  mineral 
  laumontite 
  and 
  the 
  

   trap 
  along 
  it 
  is 
  decomposed 
  ; 
  it 
  contains 
  also 
  impure 
  chlorite, 
  

   and 
  is 
  fragile 
  for 
  a 
  breadth 
  of 
  six 
  to 
  ten 
  inches. 
  A 
  similar 
  

   laumontite 
  vein, 
  but 
  nearer 
  the 
  north 
  wall 
  of 
  the 
  dike, 
  is 
  seen 
  

   at 
  Whitneyville, 
  and 
  also 
  in 
  the 
  trap 
  of 
  Whitney 
  Peak. 
  

  

  The 
  junction 
  of 
  the 
  Whitney 
  Peak 
  part 
  of 
  the 
  dike 
  with 
  

   BB' 
  takes 
  place 
  in 
  the 
  bed 
  of 
  the 
  stream 
  at 
  Whitneyville, 
  and 
  

   is 
  not 
  now 
  exposed 
  to 
  view 
  owing 
  to 
  the 
  dam 
  and 
  the 
  build- 
  

   ings 
  below 
  it.* 
  

  

  The 
  level 
  of 
  the 
  trap 
  beneath 
  the 
  dam 
  is 
  but 
  a 
  few 
  feet 
  

   above 
  and 
  below 
  tide 
  level. 
  The 
  height 
  of 
  the 
  Whitney 
  

   Peak 
  dike 
  increases 
  eastward 
  ; 
  first 
  by 
  a 
  sudden 
  rise 
  of 
  100 
  

   feet, 
  and 
  then 
  more 
  gradually 
  in 
  the 
  last 
  500 
  yards 
  to 
  280 
  

   feet. 
  Whitney 
  Peak 
  has 
  a 
  bold 
  front 
  to 
  the 
  eastward 
  with 
  

   sandstone 
  at 
  its 
  base 
  showing 
  a 
  sudden 
  stoppage 
  of 
  the 
  fissure 
  

   in 
  that 
  direction 
  ; 
  and 
  at 
  the 
  same 
  place 
  it 
  widens 
  southward 
  — 
  

   not 
  by 
  overflow, 
  as 
  the 
  precipitous 
  eastward 
  front 
  and 
  the 
  

   depth 
  of 
  the 
  trap 
  shows, 
  but 
  through 
  the 
  opening 
  of 
  a 
  trans- 
  

   verse 
  fissure. 
  The 
  Rock 
  has 
  a 
  steep 
  wall 
  70 
  to 
  80 
  feet 
  high, 
  on 
  

   the 
  north 
  side 
  of 
  the 
  summit 
  for 
  nearly 
  100 
  yards 
  ; 
  but 
  this 
  

   is 
  due 
  to 
  the 
  removal 
  of 
  the 
  sandstone 
  by 
  glacier 
  action, 
  expos- 
  

   ing 
  the 
  north 
  wall 
  of 
  the 
  trap 
  dike. 
  

  

  The 
  narrow 
  dike 
  C 
  is 
  about 
  110 
  feet 
  long. 
  It 
  is 
  situated 
  in 
  

   the 
  face 
  of 
  a 
  bluff 
  of 
  sandstone 
  ; 
  and 
  from 
  the 
  evidences 
  of 
  

   heat 
  in 
  the 
  hardness 
  of 
  the 
  rock, 
  its 
  mottled 
  and 
  light 
  gray 
  

   color 
  in 
  places, 
  its 
  steam 
  tubes, 
  and 
  epidote, 
  it 
  is 
  plain 
  that 
  the 
  

   ejection 
  determined 
  the 
  resisting 
  power 
  of 
  the 
  sandstone 
  

   against 
  denuding 
  agencies. 
  The 
  following 
  figures 
  represent 
  

  

  two 
  cross 
  sections 
  from 
  the 
  western 
  half, 
  and 
  a 
  map 
  of 
  the 
  last 
  

   10 
  feet 
  of 
  the 
  eastern 
  half. 
  At 
  65 
  feet 
  the 
  outflow 
  is 
  divided, 
  

  

  * 
  To 
  the 
  fact 
  of 
  this 
  continuation 
  I 
  have 
  recent 
  testimouy 
  from 
  Mr. 
  Eli 
  Whit- 
  

   ney, 
  who 
  has 
  superintended 
  the 
  constructions 
  made 
  there 
  during 
  the 
  past 
  forty 
  

   years. 
  Besides 
  mentioning 
  that 
  the 
  dam 
  was 
  built 
  along 
  the 
  junction 
  of 
  the 
  trap 
  

   and 
  sandstone, 
  he 
  says 
  that 
  below 
  the 
  dam 
  for 
  some 
  distance, 
  there 
  is 
  trap 
  rock 
  

   only, 
  no 
  sandstone 
  outcropping 
  there 
  to 
  his 
  knowledge. 
  

  

  The 
  gun 
  factory 
  at 
  Whitneyville 
  was 
  established 
  there 
  by 
  his 
  father, 
  the 
  in- 
  

   ventor 
  of 
  the 
  cotton-gin, 
  in 
  1798, 
  for 
  the 
  manufacture 
  of 
  muskets 
  for 
  the 
  United 
  

   States 
  Army. 
  

  

  